Technical Field
The present invention relates to a silicon-containing condensate, a composition containing the same for forming a silicon-containing resist under layer film, and a patterning process using the same.
Background Art
In 1980s, photo-exposure using g-beam (436 nm) or i-beam (365 nm) of mercury lamp as a light source had been widely used in the resist patterning. As a means for finer patterning, shifting to a exposure light having shorter wavelength was assumed to be effective, so that, for the mass production process of DRAM (Dynamic Random Access Memory) with 64 MB (work size of 0.25 μm or less) in 1990s and later ones, KrF excimer laser (248 nm), whose wavelength is shorter than i-beam (365 nm), had been used in place of i-beam as the exposure light source. However, for production of DRAM with integration of 256 MB and 1 GB or higher requiring further finer processing technologies (work size of 0.2 μm or less), a light source having a further shorter wavelength was required, and thus, a photolithography using ArF excimer laser (193 nm) has been investigated seriously over a decade. It was expected at first that the ArF lithography would be applied to the fabrication of 180 nm-node devices. However, the KrF excimer lithography survived to the mass production of 130 nm-node devices, so that a full-fledged application of the ArF lithography started from the 90 nm-node. Furthermore, mass production of the 65 nm-node devices is now underway by combining the ArF lithography with a lens having an increased numerical aperture (NA) of 0.9. For the next 45 nm-node devices, further shortening the wavelength of exposure light is progressing, and the F2 lithography with 157 nm wavelength became a candidate. However, there are many problems in the F2 lithography: cost-up of a scanner due to use of a large quantities of expensive CaF2 single crystal for a projection lens; extremely poor durability of a soft pellicle, which leads to change of an optical system due to introduction of a hard pellicle; decrease in etching resistance of a resist film, and so forth. Because of these problems, development of the F2 lithography was suspended, and ArF immersion lithography was introduced.
In the ArF immersion lithography, water having a refractive index of 1.44 is introduced between a projection lens and a wafer by a partial fill method. This enables high speed scanning, and mass production of the 45 nm-node devices is now underway by using a lens with a NA of 1.3.
For the 32 nm-node lithography, a lithography with an extreme ultraviolet beam (EUV) of 13.5 nm wavelength is considered to be a candidate. Unfortunately, the EUV lithography has problems such as needs for a higher output power of the laser, a higher sensitivity of the resist film, a higher resolution, a lower line edge roughness (LER), a non-defect MoSi laminate mask, a lower aberration of the reflective mirror, and so forth; and thus, there are innumerable problems to be solved. Development of the immersion lithography with a high refractive index, which is another candidate for the 32 nm-node, was suspended because of low transmittance of LUAG, a candidate for a high refractive index lens, and an inability to obtain a target value of a liquid's refractive index at 1.8. As mentioned above, in the photo-exposure used as a general technology, resolution based on the wavelength of a light source is approaching to its inherent limit.
In recent years, a double patterning process, in which a first pattern is formed by first exposure and development, and then a pattern is formed exactly in the space of the first pattern by second exposure, is drawing an attention as a miniaturization technology (Non-Patent Document 1). Many processes are proposed as the double patterning process. One example is a method (1) that includes forming a photoresist pattern with an interval rate of a line to a space of 1:3 by first exposure and development; processing an under layer hard mask by dry etching; laying another hard mask thereon; forming a second line pattern by subjecting the photoresist film to exposure and development at a space obtained by the first exposure; processing the hard mask by dry etching to form a line and space pattern having half pitch of the first pattern. Also, there is another method (2) that includes forming a photoresist pattern with an interval rate of a space to a line of 1:3 by first exposure and development; processing an under layer hard mask by dry etching; applying a photoresist film thereon; forming a pattern on a remaining portion of the hard mask by second exposure; and processing the hard mask by dry etching using the pattern as a mask. In both methods, the hard mask is processed by dry etching twice.
To perform the dry etching only once, there is a method in which a negative resist composition is used in the first exposure and a positive resist composition is used in the second exposure. In addition, there is a method in which a positive resist composition is used in the first exposure and a negative resist composition dissolved in higher alcohol having 4 or more carbon, in which the positive resist composition does not dissolve, is used in the second exposure.
As an alternative method, there has been proposed a method in which a first pattern formed by first exposure and development is treated with a reactive metal compound to insolubilize the pattern, and then a second pattern is newly formed between the first patterns by exposure and development (Patent Document 1).
As mentioned above, to form a finer pattern, many methods have been investigated. Among them, the common object is to prevent the collapse of a fine pattern to be formed. To accomplish this object, it is desired to further improve adhesiveness between an upper resist pattern and a resist under layer film.